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Optical Pulse Time Code Modulating Device

IP.com Disclosure Number: IPCOM000090043D
Original Publication Date: 1969-Jan-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 3 page(s) / 52K

Publishing Venue

IBM

Related People

Smith, WV: AUTHOR

Abstract

In this electrooptical scanning device, two orthogonal linear electro-optical deflection units are symmetrically placed about the center of a concentric-conjugate optical cavity to achieve high-speed scanning. In drawing 1, conjugate-concentric cavity 2 comprises parallel plane mirrors 4 and 6, each of radius R, and lenses 8 and 10. The focal length of each lens is f and the mirrors are separated by a distance equal to 4f. The effect of having such cavity is to make every object on mirror 4 imaged on mirror 6, and vice versa. Surrounding the center C of cavity 2 are two sets of deflecting plates 12 and 14, the latter disposed at right angles to plates 12. Holes 16 and 18 are drilled respectively in each mirror 4 and 6 so that such holes lie on the longitudinal axis of cavity 2.

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Optical Pulse Time Code Modulating Device

In this electrooptical scanning device, two orthogonal linear electro-optical deflection units are symmetrically placed about the center of a concentric- conjugate optical cavity to achieve high-speed scanning. In drawing 1, conjugate- concentric cavity 2 comprises parallel plane mirrors 4 and 6, each of radius R, and lenses 8 and 10. The focal length of each lens is f and the mirrors are separated by a distance equal to 4f. The effect of having such cavity is to make every object on mirror 4 imaged on mirror 6, and vice versa. Surrounding the center C of cavity 2 are two sets of deflecting plates 12 and 14, the latter disposed at right angles to plates 12. Holes 16 and 18 are drilled respectively in each mirror 4 and 6 so that such holes lie on the longitudinal axis of cavity 2.

Light to be scanned enters the center of the resonant cavity along the longitudinal axis through one of the holes, i.e., hole 16. Sinusoidal alternating voltages X and Y are applied to the deflecting plates, with the Y voltage being 90 degrees out-of-phase with respect to the X voltage. The round trip period T for light passing through the cavity equals 8f/3 x 10/-10/sec., which period is made equal to the period of the sinusoidal modulating voltage applied to such deflectors. As a result, a series of concentric circles of light is traced at each mirror, i.e., axial light, focussed again by a lens of focal length f, enters the resonator through hole 16, where successive passes of the light through halves of the resonator are labeled 0, 1, 2...p-1, p. Because of the use of a planar confocal conjugate cavity, the light being scanned goes from diffraction limited spots on mirrors 4 and 6 to parallel bundles of light rays in the region between lenses 8 and 10. The limiting aperture of the optical system is determined by the aperture d of the electrooptic deflecting system. The diffraction limited spot size omega at each mirror is approximately omega = lambda f/d.

By converting the circular scan to a parallel array of pulse-time modulated optical beams which are recombined into a single p...